Heat treating method and apparatus



March 31, 1970 J. R. LAWLER HEAT TREATING METHOD AND APPARATUS 4 Sheets-Sheet 1 (fa/77s.: law/er %VENTOR.

Filed Aug 1, 1966 March 31, 1970 J. R. LAWLER HEAT TREATING METHOD AND APPARATUS 4 Sheets-Sheet 2 Filed Aug. 1, 1966 BY a flux! Mt raw c/Zzme: F. law/er March 31, 1970 J. R. LAWLER 3,503,240

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H l J I I H March 31, 1970 J. R. LAWLER HEAT TREATING METHOD AND APPARATUS 4 Sheets-Sheet 4.

Filed Aug. 1, 1966 J r wi w mmi w Z 17 M a e P. X 7 R M R m m w J Q1 mm \i l \m Q wv/ v w 71/11/11, w mm x Q5 .l/ 1:000]. \Q o m \nfl/ A {,4 \\\\F\\% o o o o o m 0 o a m a O A United States Patent 3,503,240 HEAT TREATING METHOD AND APPARATUS James R. Lawler, 3102 Duuvale, Houston, Tex. 77042 Filed Aug. 1, 1966, Ser. No. 569,403 Int. Cl. B21b 27/06 US. Cl. 72202 22 Claims ABSTRACT OF THE DISCLOSURE The present invention relates to a method and apparatus for heat treating a metal alloy at substantially high and closely controlled temperatures. Heating is accomplished by passing a non-reactive gas in indirect heat exchange relationship with products of combustion such that the products of combustion do not directly impinge the metal alloy thereby avoiding hydrogen embrittlement and excessive scaling of the alloy. Means such as adjustable bafiles are provided to control circulation of the non-reactive gas into contact with the metal strip thereby providing close control of temperature.

The present invention relates to an improved heat treating method and apparatus and, more particularly, an improved heat treating method and apparatus for heating and forming metal strips into various structural shapes, for example, titanium alloy strips into structural configuration such as Cs, Zs, Us, and the like.

It would be desirable to provide a heating and structure forming method and apparatus in which metal alloy strips are formed into structural configurations of tight bend radii, and which include good tolerance control and metallurgical integrity of formed parts. It would also be desirable to provide such a heating and forming system and method which would minimize or prevent hydrogen embrittlement and excessive scaling of metal alloys such as titanium, at elevated temperatures and, if desired, such a method and system which can be sealed and a gas unreactive to the metal alloy could be utilized to prevent contamination. The present invention is directed to such a method and apparatus.

It is therefore an object of the present invention to provide a method of and an apparatus for forming metal alloy strips into structural configurations of relatively tight bend radii with metallurgical integrity of the formed parts.

Yet a further object of the present invention is the provision of such a method and apparatus in which metal alloy strips are formed into structural configurations of relatively tight bend radii in which hydrogen embrittlement is minimized or eliminated.

A further object of the present invention is the provision of such a heating method and apparatus in which metal alloy strips are formed into structural configurations of relatively tight bend radii without excessive scaling even at elevated temperatures.

Yet a further object of the present invention is the provision of a method of and an apparatus for forming metal alloy strips into structural configurations in which the strips are heated by a nonreactive gas which is heated by indirect heat exchange relationship with products of combustion and the products of combustion do not directly impinge the metal alloy strips.

A further object of the present invention is the provision of an apparatus for forming strips of metal alloy into structural configurations of tight bend radii without hydrogen embrittlement and undue scaling at elevated temperatures in which temperature throughout the structural configuration forming stations is controlled at least in part by adjustable baffle means controlling the flow of heating gas to each forming station.

Yet a further object of the present invention is the ice provision of a method and apparatus for heating and forming metal alloy strips into structural configurations of tight bend radii in which the formed structural configurations are within close tolerances and in which a bend radii as tight as two times the thickness of the metal strips can be maintained, if desired.

Other and further objects, features and advantages of the invention will be apparent from the following description of presently-preferred embodiments thereof, given for the purpose of disclosure, and taken in conjunction with the accompanying drawings, and where,

FIGURE 1 is a side view of a structural configuration forming furnace according to the invention,

FIGURE 2 is a plan view of the furnace of FIGURE 1,

FIGURE 3 is a sectional view taken along the line 3-3 of FIGURE 1,

FIGURE 4 is a sectional view taken along the line 44 of FIGURE 3,

FIGURE 5 is a sectional view taken along the line 55 of FIGURE 2,

FIGURE 6 is a sectional view taken along the line 66 of FIGURE 5, and

FIGURE 7 is a side view of the main oven illustrating a power drive for pairs of forming rolls.

Referring now to the drawings, and particularly to FIGURE 1, the furnace includes an elongate preheating oven or furnace 10 and an elongate main oven or structural configuration forming furnace 12. The preheating oven 10 and the main oven 12 are arranged in end to end relationship and are supported by suitable supporting structure 14 and 16, respectively. Since any desired structural support for these ovens may be utilized no detailed description thereof is deemed necessary or given.

As best seen in FIGURES 3 and 4, to which reference is now made, the preheating oven or furnace 10 generally includes an insulated body 18 which includes the fire tube chamber 20 and the preheating metal strip chamber 22 separated by the longitudinally extending wall member or partition 24 which is provided with a series of spaced openings 26 along its length. The adjustable bafiles 28 are disposed in the spaced openings 26, the bafi'les being externally controlled by means of the handles 31 (only one being shown in FIGURE 4) at the ends of the shafts 33 upon which the bafiles 28 are mounted. Thus, the flow of heated gas, such as air, from the fire tube chamber 20 into the preheating strip chamber 22 is controlled by means of adjusting the handles 30 and thus the amount of each opening 26 in the partition 24.

The partition 24 stops short of the end of the body 18 adjacent to it to thus permit circulation of heating gas into the preheat strip chamber 22 at that end and in the direction of the arrows.

Disposed within the fire tube chamber 20 is the finned heating tube 30 through which a heating medium capable of high temperature, such as products of combustion, flow to provide the necessary and desired heat. For example, a pressure type gas burner nozzle 32 is provided adjacent one end of the fire tube 30 and is exhausted out the other end of the fire tube 30 at the exhaust 35.

As best seen in FIGURE 1, a centrifugal type circulating fan 34 is provided which is driven by the variable speed motor 36 and driven belt 38 which provides a flow of air into the passage 40, and with reference again to FIGURE 3, circulates the air along the length of the fire tube 30, through the baffled openings 26, and back through the strip chamber 22 out the outlet 42 and back to the circulation fan 34 in the direction of the arrows, as illustrated. If desired, the heated gas may be exhausted rather than recirculated.

The gas while flowing along the fire tube is heated and the temperature along the length of the preheat strip oven is controlled by means of adjusting the baffles 28 thereby controlling the flow of hot gas into the strip chamber 22.

Disposed within the preheat strip oven 22 is a lOngitudinally extended guide channel 44 which'extends out each end of the body 10 and receives the strip alloy which is moved through the preheat strip oven 22. The guide member 44 may take any desired shape but should be such to guide and support the alloy metal strip as it is moved through the preheat oven.

Disposed along the length of the preheat strip oven 22 are a plurality of thermocouples 46 which are electrically connected, such as shown in the dotted lines and generally designated by the reference letter A, to temperature indicating means, such as the temperature strip recorders on the control panel 48 and similarly designated by the reference letter A.

Thus, the multipoint recorder A keeps a continuous record of the heat within the preheat strip oven at intervals along its length by which close control of the heat can be obtained by making adjustments in the openings 26 by exteriorly adjusting the baffles 28.

Referring now to the main oven or furnace 12 and, as best seen in FIGURES and 6, the main oven 12 is divided generally into fire tube compartment 50 and a strip compartment 52. The fire tube compartment includes the finned fire tube 54 which extends lengthwise in the fire tube compartment 50 and then returns to the exhaust 56. A pressure combustion nozzle 58 fires into the inlet end 60 of the fire tube 54 for circulation of products of combustion in the fire tube and out the exhaust 56.

Extending longitudinally of and transversely across the fire tube oven 54 is a wall like baffle member 62 which extends between the entering portion and return portion of the fire tube 54. As best seen in FIGURE 5, this baflie member 62 extends completely across the fire tube chamber 50 but does not extend to each end thereof. Adjacent the entrance end of the fire tube chamber is another wall like baffie member 64 which extends from the end of the bafile member 62 annularly and downwardly to the upper wall member or partition 66 which separates the fire tube chamber 50 and structural configuration forming chamber 52.

The partition 66, as previously mentioned, extends lengthwise and transversely of the body of the main oven 12 dividing it into the fire tube compartment 50 and the metal strip forming oven 52 and is provided with a plurality of openings 68 which are provided with the adjustable baflies 70, which are the same in construction as those shown in FIGURES 3 and 4 and which are also provided with handles so that they may be readily adjusted externally for control of the flow of the heated gas from the fire tube chamber 54 and, accordingly, the temperature is closely controlled at each of the structural configuration forming stations presently to be described.

Referring again to FIGURE 1, the circulating fan 72 is provided adjacent the inlet end of the main oven which is driven by the variable speed motor 74 and driving belt 76.

Referring again to FIGURE 5, the circulating fan 72 is provided with the outlet 75 which is connected to the inlet 77 of the fire tube chamber 54. The circulation of gas follows the arrows illustrated in FIGURE 6 and flows over the inlet and outlet portions of the finned fire tube 54 and then along the length of the fire tube in the upper fire tube compartment and then along the fire tube in its lower compartment and is returned to the circulating fan by the return duct generally indicated at 78. I

As previously mentioned, by adjusting the baffles 68 by moving their handles very accurate and close control of the temperature can be maintained in each of the work forming stages in the main strip oven 52.

A plurality of thermocouples are disposed in the main strip oven and preferably at each of the work stages. For convenience of reference, the thermocouples are shown in dotted lines with dotted leads indicated by the reference numerals 1-8 and are connected to the temperature indicating means on the control panel similarly indicated by corresponding numerals 1 through 8. This insures very close and accurate control of the temperature at each of the work forming stages as the temperature is indicated at each station and is controlled by adjusting the adjustable baflles near or at the particular stage.

Similarly, a thermocouple is provided closely adjacent the finned fire tube 60 which, again, for convenience of reference, is shown in dotted lines to the lead B which is connected into the control panel 48 and is similarly indicated by the reference letter B. Thus, very close and accurate control of the temperature in the main oven is maintained.

A guid strip 80 is provided which is aligned with the guide strip 22 of the preheat oven 10 and receives the preheated metal strip and guides it to a series of work stations, here indicated as eight in number, although any desired number can be used.

A series of work supporting and guide members 82a-g, inclusive, are provided, which receive the preheated metal strip and support it as it is moved through a series of structural configuration forming rolls 84a-i, inclusive. The pairs of rolls 84ai, inclusive,'rnay be of any desired shape so that the metal strip is progressively formed into the desired shape, such as US, Zs, Us, channels and the like. 1

'The pairs of rolls 84a-i, inclusive, are externally and adjustably mounted in the bearing blocks 86, as best seen in FIGURE 6, illustrating the pair of rolls 84c i'otata'bly journalled in the bearing blocks 86. Of course, similar bearing blocks or supports are utilized for each I of the other pairs of rolls. As illustrated in FIGURE 6,

the lower roll of the pair of rolls 84e is not adjustable, but the upper one of these rolls is adjustable for bringing it closer or farther from the lowermost rolls by means of turning the micrometer adjusting screws 88.

Each pair of rolls 84 have matching structural configuration shaping rolls, as best seen on FIGURE 6, so that as the strip of alloy progresses through the structural configuration forming main oven it is progressively formed into desired structural shapes.

For use in high temperatures, the rolls may be cooled by a suitable cooling medium, and as illustrated in FIG URE 5, each of the pairs of rolls 84a-i, inclusive are hollow which provides a passage for cooling liquid which is circulated through the inlets 92 and the outlets 94 to a suitable source of cooling fluid, not shown.

As illustrated in FIGURE 7, each of the pairs of rolls 84a-i are power driven by the motor 96 which through the reduction gears 97, 98 and 99 drive the gear chains 100 and .101 which mesh with the gears 102 and 103, respectively, see FIGURE 2, and drive the rolls 84q-i. The idlers 104 and 105 are provided for the gear chains 100 and 101, respectively. Preferably the motor 96 should be a variable speed motor and should be variably mounted. A 25 h.p. motor is satisfactory. No more description of the power drive for the pairs of rolls 84a-i is set forth or deemed necessary since any preferred driv for the pairs of rolls 84a-i may be used.

No more detailed description of the pairs of rolls which shape the metal alloy strip into structural configurations amples thereof are illustrated in my copending application, Ser. No. 569,404, filed concurrently with this application.

The thermocouples which are used may be of any desired type. Satisfactory thermocouples are Megopak type contact thermocouple assemblies. These thermocouples may be ten inches, have a miniature connection head, be provided in a stainless steel sheaf with an integral hot junction. The thermocouples may be connected to any desired temperature indicating means, such as a Honeywell electronic strip chart recorder, although any type of thermocouple assembly and temperature recording or indicating means may be utilized.

The circulating fans 34 and 72 may be 5 hp. variable speed motor driven high temperature centrifugal type circulating fans.

The pressure burners 32 and 58 are preferably controlled by a proportioning type control, not shown, in response to signals from the thermocouples B and C, re spectively.

If desired, the controls can all be manual, or if preferred, may be automatic in response to temperature signals at various parts of the apparatus.

While the preheat oven and main oven may be made of any suitable materials and insulation, preferably, the members are stainless steel or stainless steel lined for high temperature work and are provided with suitable insulation for high or elevated temperatures.

In operation, strips of metal alloys, such as titanium, are fed into the entrance of the guide 22 where it is preheated to any preferred temperature. For example, for titanium strips, the preheat over 22 preferably is heated to a temperature in the range of from about 1450 F. to about 1500 F. This is accomplished by firing products of combustion from the nozzle 22 into the finned fire tube 30 and circulating nonreactive gas along the length of the finned fire tube, back along the strip and out the return 42 back to the circulation fan 34. By proper adjustment of the adjustable baffles 28, the temperature within the preheating strip chamber is closely controlled and adjusted along its length. For the temperature in the preheat chamber 22 can be readily maintained in the range of about 1100 F. to about 1500 F. If desired the metal strip can be left in the preheat chamber 22 long enough to anneal it or to just bring it up to temperature.

The metal alloy strip leaves the preheating chamber 22 and enters the main oven 12 and moves along the guide 80 onto the guide support 82a and then is formed by means of the forming rollers 84a-i, inclusive, progressively into structural forms which may be of very tight bend radii. For example, with titanium, tight bend radii is obtained up to two times the thickness of the material. The pressure-fired burner provides the desired heat into the finned fire tube 54 and out the exhaust stack 56. The circulating fan 72 introduces gas into the fire tube chamber 50 and circulates it along the length of the finned tube 54 and back along its length and out the return 78 to the fan 72. By adjusting the adjustable bafiles 68 very close control of the temperature is maintained at each of the stations along the length of the main strip oven. For example, for producing hot roll formed titanium parts on a continuous basis at speeds up to 60 feet per minute and maintaining part tolerances desired, the temperature tolerances may be maintained plus or minus 50 F. in a range from 1100 F. to 1500 F. throughout the roll forming process.

On annealed or duplex annealed titanium strips from eight feet long up to coils, structural configurations, for example Z sections, tolerances of plus of minus .010 and plus or minus 2 on angles with bend radii as tight as two times metal thickness were maintained.

There is no direct application of the products of combustion to the metal strips which avoid hydrogen embrittlement and excessive scaling. Also, the entire system may be sealed and an unreactive gas may be used, if desired. Air may be used as the circulated gas when unreactive to the metal alloy being used. Good results have been obtained with air when shaping titanium.

Disposed at the outer end, as shown in dotted lines, is a slide type door 110, which is opened when the formed metal strips is discharged from the main oven 12. If desired, a power straightener, not shown, may be utilized to straighten the formed metal strips as they emerge from the main strip oven 52.

The method of the invention includes the steps of heating the metal alloy strips to the desired temperature range, such as 1100 F. to 1500 F. by an indirect heat exchange relationship in which the products of combustion utilized to provide the heat do not directly impinge the metal alloy strips but a heating medium, such as air or a nonreactive gas is circulated about the alloy metal strips thereby avoiding hydrogen embrittlement and excessive scaling. The method includes the step of progressively forming the alloy metal strips into structural configurations while being so heated.

In the method of the invention, the apparatus previously described and illustrated in the drawings may be utilized. Similarly, the structural configuration forming rolls illustrated in the apparatus of the invention and disclosed in my copending application, previously referred to, may be utilized. Any type of oven arrangement and structural forming means may be utilized, however, in which there is no direct impingement of the alloy strips by the products of combustion utilized to provide the heat, but air or some other nonreactive gas is utilized which is circulated about a closed fire tube containing these products of combustion thereby heating the air or other nonreactive gas and then circulating it about the metal alloy strip to bring it to the desired temperature.

The present invention therefore is well suited and adapted to attain the objects and ends and has the advantages and features mentioned as well as others inherent therein.

While only presently-preferred examples and embodiments of the invention have been given for the purpose of disclosure, changes in details of the apparatus, arrangement of parts and in the method may be made which are within the scope of the invention as defined by the appended claims:

What is claimed is:

1. A furnace for forming a metal alloy into a structural configuration comprising,

an oven provided with a fire tube chamber and a structural configuration forming chamber,

a fire tube in the fire tube chamber,

means for progressively forming the metal alloy into the structural configuration in the structural configuration forming chamber,

means for circulating a gas about the fire tube thereby heating the gas and then about the means in the structural configuration chamber, and

adjustable means controlling the circulation of gas into the structural configuration forming chamber thereby controlling the temperature therein.

2. The furnace of claim 1 including means for introducing products of combustion into the fire tube. A

3. The furnace of claim 1 including a plurality of baffies adjustably disposed in openings between the fire tube chamber and the structural configuration forming chamber arranged for controlling the circulation of gas into the structural forming chamber.

4. A furnace for forming a metal alloy into a structural configuration comprising,

an elongate oven,

a partition extending along the length of the oven forming it into a fire tube chamber and into a structural configuration forming chamber,

a fire tube extending into and out of the fire tube chamber,

means for introducing products of combustion into the fire tube thereby heating it,

means for progressively forming the metal alloy into the structural configuration in the structural configuration forming chamber,

the partition being provided with a plurality of openings, bafiles adjustably mounted in each of the openings for controlling the flow of heated gas fromv the .fire tube chamber into the structural configuration chamber,

means for introducing gas into the fire tube chamber thereby providing the heated gas and for exhausting the heated'gas flowing from the fire tube chamber into the structural configuration chamber,

means for introducing the metal alloy into the structural configuration chamber, and

means for discharging the metal alloy formed into the structural configuration from the structural configuration forming chamber.

5. The furnace of claim 4 where the means for progressively forming the metal alloy into the structural configuration comprises a plurality of structural configuration forming rolls.

6. The furnace of claim 4 including temperature indicating means disposed in the fire tube chamber and in the structural configuration forming chamber indicating the temperatures thereof.

7. The furnace of claim =4 where the means for introducing the metal alloy into the structural configuration forming chamber includes an elongate guide extending lengthwise therein, where the means for progressively forming the metal alloys into structural configuration comprise a plurality of spaced pairs of rolls disposed adjacent an inner end of the guide,

and includes support guide members between each of the pairs of rolls.

8. A furnace comprising,

an elongate oven,

a partition extending along the length of the oven forming it into a fire tube chamber and into a heating chamber,

a fire tube extending into and out of the fire tube chamber,

means for introducing products of combustion into the fire tube thereby heating it,

the partition being provided with a plurality of openmgs,

baffles adjustably mounted in each of the openings controlling the flow of heated gas from the fire tube chamber into the heating chamber, means for introducing gas into the fire tube chamber thereby providing the heated gas and for exhausting the heated gas flowing into the heating chamber,

means for introducing a metal alloy into the heating chamber, and

means for discharging the metal alloy after being heated from the heating chamber. 9. The furnace of claim 8 including temperature indicating means disposed in the fire tube chamber and in the heating chamber indicating the temperature therein.

10. The furnace of claim 8 including a guide extending through the length of the heating chamber for guiding the metal alloy therethrough.

11. A furnace for forming a metal alloy into a structural configuration comprising,

an elongate preheating oven, a first partition extending along a substantial portion of the length of the preheating oven forming it into a fire tube chamber and a preheating chamber,

an elongate product forming oven,

a second partition extending substantially along the length of the product forming oven forming it into a fire tube chamber and a structural configuration forming chamber, I

a fire tube extending into and out of each of the fire tube chambers,

means for introducing products of combustion into each of the fire tubes thereby heating them,

the first partition and the second partition each being provided with a plurality of openings,

bafiles adjustably mounted in each of the openings controlling flow of gas from the fire tube chambers into the preheating chamber and the structuralconfigura- .tion forming chambers,

the preheating chamber and the structural configuration forming chamber arranged in end to end relationship with one another,

a first guide extending through the preheating chamber for guiding the metal alloy therethrough while preheating it,

a second guide extending into the structural configuration chamber aligned with the first guide receiving the-preheated. metal alloy from the preheating chamber,

-means for progressively forming the metal alloy into the struutural configuration in the structural configuration forming chamber,

means for discharging the metal alloy so formed into the structural configuration from the structural configuration forming chamber, and

means for circulating gas about each of the fire tubes, through the 'bafiles openings and into the preheating oven and into the structural configuration oven.

12. The furnace of claim 11 where the means for progressively forming the metal alloy into the structural configuration comprises a plurality of spaced pairs of rolls and,

includes guide and support means between the pairs of rolls guiding and supporting the metal alloy as it moves between the pairs of rolls. 13. The furnace of claim 12 including temperature indicating means in each of the fire tube chambers and spaced along each of the preheating chamber and the structural configuration chamber.

14. A method of forming a metal alloy into a structural configuration comprising,

heating the metal alloy to a temperature Where it can be formed into the structural configuration by circulating a gas which does not react with the metal alloy over a heat source and in indirect heat relationship therewith thereby heating the gas and then circulating the heated gas about the metal alloy, and

progressively forming the metal alloy into the structural configuration while being so heated.

15. The method of claim 14 including controlling the temperature of the metal alloy by controlling the flow of the heated gas thereto.

16. The method of claim 15 including maintaining the temperature in the range of from about 1100 'F. to about 1500 F.

17. A method of forming a metal alloy into a structural configuration comprising,

heating the metal alloy to a temperature where it can be formed into the structural configuration by heating a gas unreactive to the metal alloy by indirect heat relationship with products of combustion and then circulating the heated gas about the alloy metal, and

- progressively forming the alloy metal into the structural configuration while being so heated.

18. The method of claim 17 including controlling the temperature of the metal alloy by controlling the flow of the heated gas thereto.

19. The method of claim 18 Where the temperature is maintained in the range of from about 1100F. to about 1500F.

20. A furnace for forming a metal alloy into a structural configuration comprising,

an oven provided with a fire tube chamber and a structural configuration forming chamber,

a fire tube in the fire tube chamber, means for progressively forming the metal alloy into the structural configuration in the structural configuration forming chamber, said means including,

a plurality of structural configuration forming rolls,

said rolls being journalled in bearing blocks, the blocks being mounted externally of the structural configuration forming chamber, and

means for circulating a cooling medium through said forming rolls,

means for circulating a gas about the fire tube thereby heating the gas and then about the means in the structural configuration chamber, and

adjustable means controlling the circulation of gas into the structural configuration forming chamber thereby controlling the temperature therein.

21. The furnace of claim 20 including a plurality of bafiles adjustably disposed in openings between the fire tube chamber and the structural configuration forming chamber arranged for controlling the circulation of gas into the structural forming chamber.

22. The furnace of claim 20 including temperature indicating means disposed in the fire tube chamber and in in the structural configuration forming chamber indicating the temperatures thereof.

References Cited UNITED STATES PATENTS CHARLES W. LANHAM, Primary Examiner E. M. COMBS, Assistant Examiner US. Cl. X.R. 

